1. Field of the Invention
The present invention relates to a drive system, in particular for a vehicle, comprising an electric machine, by means of which a drive shaft of a drive assembly is capable of being driven in rotation and/or electric energy is capable of being recovered during the rotation of the drive shaft. The electric machine has a stator arrangement and a rotor arrangement connected or connectable to the drive shaft for joint rotation about an axis of rotation.
2. Discussion of the Prior Art
A drive system of this type, in which the rotor arrangement is excited permanent-magnetically, is known from German reference DE 196 31 384 C1. When drive systems of this type are being assembled or dismantled, there is the problem that, because of the permanent-magnetic excitation of the rotor arrangement and because of the relatively small airgap between the rotor arrangement and the stator arrangement, said airgap then being formed in the assembled state, when a system of this type is being mounted with a high degree of precision, care must be taken to ensure that the rotor arrangement does not come into contact with the stator arrangement, since, because of magnetic attraction, these would then immediately adhere to one another and could ultimately no longer be separated or, if such separation were to take place, there would be a great risk that one of the subassemblies would be damaged. Even in the case of rotor arrangements not excited permanent-magnetically, there is the problem that if there is insufficiently accurate guidance during the axial relative movement between the rotor arrangement and stator arrangement, the various subassemblies may be damaged due to mutual contact and to their sliding on one another.
The object according to the present invention is, therefore, to design a generic drive system in such a way that, when relative movements between the rotor arrangement and stator arrangement are carried out, for example when the electric machine is assembled or dismantled, mutual contact between these two subassemblies can be avoided.
This object is achieved, according to the present invention, by means of a drive system, in particular for a vehicle, comprising an electric machine, by means of which a drive shaft of a drive assembly is capable of being driven in rotation and/or electric energy is capable of being recovered during the rotation of the drive shaft. The electric machine has a stator arrangement and a rotor arrangement connected or connectable to the drive shaft for joint rotation about an axis of rotation.
Furthermore, in this drive system according to the invention, a positive guidance arrangement is provided, by means of which the rotor arrangement and the stator arrangement are guided relative to one another when a relative axial movement is carried out in order to assemble or dismantle the electric machine.
Care is therefore taken, by the provision of the positive guidance arrangement, to ensure that, when a relative axial movement is carried out between the rotor arrangement and the stator arrangement, mutual contact between these subassemblies in the critical regions, that is to say the region of interaction, is necessarily avoided. As a result, the mounting operation can be carried out in a markedly simpler way, for example even by hand, without the use of precision-guidance machine tools.
According to a first embodiment, the drive system according to the invention may be designed such that the positive guidance arrangement comprises a positive guidance unit and such that positive guidance interaction is generated between the rotor arrangement and the positive guidance unit positioned or positionable in a predetermined position on the drive shaft. At the same time, there may, for example, be provision for the positive guidance unit to be positioned or positionable in the predetermined position before the rotor arrangement is moved axially up to the stator arrangement, and for a guidance portion of the rotor arrangement to be capable of being guided along the positive guidance unit. In order to simplify the mounting operation, but make sure that no unintended rattling noises or unbalances occur during rotary operation, it is proposed that, after the axial guidance of the rotor arrangement relative to the stator arrangement has taken place, the positive guidance unit is held together with or by the rotor arrangement on the drive shaft. Alternatively, however, it is also possible, after axial guidance of the rotor arrangement relative to the stator arrangement has taken place, for the positive guidance unit to be capable of being removed from the region of the rotor arrangement.
The exact positioning of the positive guidance unit relative to the drive shaft and therefore exact positioning of the rotor arrangement relative to the stator arrangement can be obtained by the provision, on the drive shaft, of a positioning arrangement, by means of which the positive guidance unit is positioned or positionable in the predetermined position relative to the drive shaft.
According to a further embodiment of the present invention, there may be provision for the positive guidance arrangement to be designed for generating positive guidance interaction between the stator arrangement and the rotor arrangement. This may be implemented in that the positive guidance arrangement comprises a first positive guidance region on the stator arrangement and a second positive guidance region on the rotor arrangement. The second positive guidance region is guided along the first positive guidance region during relative axial movement between the stator arrangement and rotor arrangement. There may be provision, for example, for the first positive guidance region to comprise a first positive guidance portion on the stator arrangement and for the second positive guidance region to comprise a second positive guidance portion on a portion of the rotor arrangement connected or connectable to the drive shaft.
In an arrangement in which positive guidance occurs between components or subassemblies which, during subsequent operation, then have to be movable relative to one another, there is the problem that, because of the low tolerances in the region of positive guidance, abrasion or impact could then occur during rotary operation, even when the unevenness of movement is only minimal. In order to avoid this, it is proposed that, when the electric machine is being assembled, the first and second positive guidance portions provide essentially no positive guidance between the stator arrangement and the rotor arrangement in an end region of the relative axial movement of the rotor arrangement with respect to the stator arrangement.
However, even in an embodiment of this type, care must be taken to ensure that, during the entire axial movement action, mutual contacting between the rotor arrangement and stator arrangement is avoided in the critical regions. This may then be achieved, for example, by the positive guidance arrangement comprising a third positive guidance region and, in the end region of the relative axial movement, by the first positive guidance region and/or the second positive guidance region providing, together with the third positive guidance region, positive guidance of the stator arrangement relative to the rotor arrangement.
A practical embodiment which can be made up in a particularly simple way may be obtained, here, if the third positive guidance region is provided on the drive shaft and comprises a third positive guidance portion, and if the second positive guidance region on the rotor arrangement comprises a fourth positive guidance portion for interaction with the third positive guidance portion. Alternatively or additionally, however, there may be provision for the third positive guidance region on a fixed component, preferably the drive assembly, to comprise a third positive guidance portion, and for the first positive guidance region to comprise a fourth positive guidance portion, preferably formed by the first positive guidance portion, for interaction with the third positive guidance portion on the fixed component.
So that no additional components or subassemblies have to be provided for the positive guidance function, but, instead, so that already existing components or parts thereof can be used, it is proposed that the first positive guidance region comprises as the first positive guidance portion a surface region, preferably an inner surface region, on a stator carrier of the stator arrangement, and that the second positive guidance region comprises an essentially cylindrical portion of the rotor arrangement, said portion being displaceable at least with a surface region, preferably an outer surface region, as a second positive guidance portion, along the first positive guidance portion.
There may also be provision for the third positive guidance region to comprise an axial projection on the drive shaft, with a surface region, preferably an outer surface region, as the third positive guidance portion, and for the second positive guidance region to comprise as the fourth positive guidance portion, a surface region preferably an inner surface region, of an essentially cylindrical portion of the rotor arrangement.
Alternatively or additionally, it is again possible, here too, for the third positive guidance region to comprise as the third positive guidance portion a surface region, preferably an outer surface region, of a fixed component, and for the first positive guidance region to comprise as the fourth positive guidance portion a surface region, preferably inner surface region, of the stator arrangement.
In order, at the same time, to make a uniform relative axial movement possible, it is proposed that the third positive guidance portion and the second positive guidance portion comprise surface regions adjoining one another essentially flush.
The positive guidance concept according to the invention may, as illustrated above, be based on first mounting one of the subassemblies, namely the rotor arrangement and the stator arrangement, and then moving the other up to it. Although this is a particularly practical concept, it is also conceivable, however, for systems of this type to be produced by a supplier and then be attached as a complete unit to the drive assembly. According to a further aspect of the present invention, therefore, it is proposed that, after relative axial movement between the rotor arrangement and the stator arrangement has been carried out for assembling the electric machine, the rotor arrangement and the stator arrangement are combined to form a premounted subassembly.
According to a further embodiment of the present invention, there may be provision for the positive guidance arrangement to be designed for generating positive guidance interaction between the rotor arrangement and a fixed component. In this case, it is advantageous if the fixed component is provided on the drive assembly. A small axial overall size of an entire drive for a vehicle is obtained in this way.
In this embodiment of a system according to the invention, there may then be provision for the fixed component to comprise or form a first positive guidance region and for the rotor arrangement to comprise a second positive guidance region which is guided along the first positive guidance region during relative axial movement between the rotor arrangement and the stator arrangement. For example, the first positive guidance region may comprise a first positive guidance portion, and the second positive guidance region may comprise a second positive guidance portion for interaction with the first positive guidance portion.
Here too, a system is provided again, in which positive guidance occurs between subassemblies which must move relative to one another during subsequent rotary operation. In order once again to avoid the situation where these two subassemblies unintentionally abrade one another or come into contact during rotary operation, it is proposed that, when the electric machine is being assembled, the first and the second positive guidance portions provide essentially no positive guidance between the stator arrangement and the rotor arrangement in an end region of the relative axial movement of the rotor arrangement with respect to the stator arrangement.
Since it is nevertheless advantageous, even in this embodiment, to ensure positive guidance over the entire axial movement, up to the finished mounting position, it is proposed that the positive guidance arrangement comprise a third positive guidance region, and that the first positive guidance region and/or the second positive guidance region provide, together with the third positive guidance region, positive guidance of the stator arrangement relative to the rotor arrangement in the end region of the relative axial movement.
For this purpose, for example, the makeup may be such that the third positive guidance region is provided on the drive shaft and comprises a third positive guidance portion, and such that the second positive guidance region on the rotor arrangement comprises a fourth positive guidance portion for interaction with the third positive guidance portion.
An embodiment to be implemented particularly easily may be obtained if the third positive guidance region comprises an axial projection on the drive shaft, with a surface region, preferably an outer surface region, as the third positive guidance portion, and if the second positive guidance region comprises as the fourth positive guidance portion a surface region, preferably an inner surface region, of an essentially cylindrical portion of the rotor arrangement.
There may also be provision for the first positive guidance region to comprise as the first positive guidance portion a surface region, preferably an inner surface region, of the fixed component, and for the second positive guidance region to comprise as the second positive guidance portion a surface region, preferably an outer surface region, of an essentially cylindrical portion of the rotor arrangement.
The present invention is particularly suitable for use in systems in which, when the electric machine is in the assembled state, the stator arrangement and the rotor arrangement are arranged so as to overlap one another axially, at least in regions.
According to a further alternative embodiment, the positive guidance may be obtained in that the positive guidance arrangement comprises a positive guidance element which, before the rotor arrangement and the stator arrangement are moved axially toward one another, can be arranged on a rotor-arrangement surface region to be positioned facing the stator arrangement or can be arranged on a stator-arrangement surface region to be positioned facing the rotor arrangement. This positive guidance element ensures that, when the relative axial movement is carried out, the critical regions of the two subassemblies, namely the rotor arrangement and the stator arrangement, cannot come directly into contact with one another, but are separated by the positive guidance element. As a result, on the one hand, damage to the two subassemblies is avoided and, on the other hand, care is taken to ensure that, particularly in the case of permanent-magnetically excited rotor arrangements, because of the interspace which is maintained the magnetic attraction forces which occur do not become so high that further axial displacement of the two subassemblies relative to one another will no longer be possible.
For example, there may be provision for the positive guidance element to be essentially hollow-cylindrical and to be produced preferably from elastic material.
A particularly simple embodiment to be implemented cost-effectively may be obtained if the positive guidance element has a net-like structure.
In order, on the one hand, to ensure that the necessary positive guidance is generated with the desired effect of minimizing or keeping low the magnetic interaction which occurs, but, on the other hand, also to allow manual assembly, it is proposed that the positive guidance element have a thickness which is slightly smaller, preferably approximately 0.2 mm smaller, than an airgap formed between the rotor arrangement and the stator arrangement after the axial movement toward one another has taken place.
The use of a positive guidance element of this type, which protectively surrounds the rotor arrangement or the stator arrangement, is particularly advantageous because, after mounting has taken place, this positive guidance element can then be removed and therefore no components serving for positive guidance have to be left on the drive system, and, furthermore, this positive guidance element can be used for a further mounting operation.
The present invention relates, furthermore, to a method for assembling or/and dismantling a rotor arrangement and a stator arrangement of an electric machine, by means of which electric machine a drive shaft of a drive assembly is capable of being driven in rotation and/or electric energy is capable of being recovered during the rotation of the drive shaft. The method including moving the rotor arrangement and the stator arrangement relative to one another in the direction of an axis of rotation, during which relative movement the rotor arrangement and the stator arrangement are positively guided relative to one another.
As already referred to above, in a method of this type, the procedure may be such that, before the relative axial movement between the rotor arrangement and stator arrangement is carried out, the rotor arrangement is mounted on the drive shaft or the stator arrangement is mounted on a fixed subassembly, preferably the drive assembly.
Alternatively, for providing a premounted subassembly, it is possible for the relative axial movement between the rotor arrangement and the stator arrangement for assembling the electric machine to be carried out before the rotor arrangement is mounted on the drive shaft and before the stator arrangement is mounted on a fixed subassembly, preferably the drive assembly.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.